Nicotine is an agonist at which receptors?

• A. Dopamine D2 receptors
• B. GABA receptors
• C. Muscarinic acetylcholine receptors
• D. Nicotinic acetylcholine receptors

Answer: (D)

Nicotine acts as an agonist at nicotinic acetylcholine receptors. These are ligand-gated ion channels found in the brain, autonomic ganglia, and at the neuromuscular junction. When nicotine binds, the channel opens and lets cations enter, depolarizing the cell and triggering transmitter release. In the brain, activating these receptors on dopamine neurons elevates dopamine in reward pathways, helping explain nicotine’s reinforcing effects. This is different from dopamine D2 receptors (which are dopamine GPCRs), muscarinic acetylcholine receptors (acetylcholine GPCRs), or GABA receptors (inhibitory chloride channels). Nicotine directly targets nicotinic acetylcholine receptors, not the other receptor types listed.